Micromechanically manufactured high-frequency short-circuiting switches are made up of a thin metal bridge stretched between the ground lines of a coplanar waveguide. This bridge is electrostatically drawn to a thin dielectric disposed on the signal line, thereby increasing the capacitance of the plate-type capacitor formed by the bridge and the signal line. This capacitance between the signal line and the ground line influences the propagation properties of the electromagnetic waves guided on the waveguide. In the off state (the metal bridge is below), a large part of the power is reflected. In the on state (the metal bridge is above), a large part of the power is transmitted.
The device of the present invention has the advantage that the length of the metal bridge, i.e., the length of the second electrically conductive connection, is not dependent on the spacing of the ground lines of the coplanar waveguide, i.e., the spacing of the ground lines of the waveguide may be selected independently of the length of the second connection and vice versa. This results in the advantage that a high-frequency microswitch having the features, xe2x80x9cminimal spacing of the ground lines,xe2x80x9d xe2x80x9chigh operating frequency,xe2x80x9d xe2x80x9clarge expansion of the second line, i.e., of the metal bridge,xe2x80x9d and xe2x80x9clow switching voltagexe2x80x9d is easily produced in accordance with the present invention. Furthermore, it is possible that the inductor serially-connected to the capacitor by the first electrically conductive connection between the ground lines of the coplanar waveguide is selected independently of the design of the signal line. As a result, it is possible using simple means to achieve a low obstruction of the propagation of the electromagnetic waves along the waveguide as well as optimal dimensioning of the first connection designed as a short-circuiting link between the ground lines and the waveguide.
It is also advantageous that the first and the second connections are metallic connections. As a result, all of the material-specific and process technology-related advantages of using metals as electrically conductive connections find a use in accordance with the present invention.
It is also advantageous that the second connection is mechanically deformable such that the spacing of the first connection and the second connection is variable in at least one partial area of the second connection. As a result, a capacitor having a variable capacitance is produced using simple means.
It is also advantageous that the capacitance of the capacitor is able to be changed by an electrostatic force between the first connection and the second connection. Therefore, simple means are able to be used to provide two circuit states of the device of the present invention, so that a reliable and quick switchability of the device is ensured. Moreover, as a result, the circuit state of the device is always clearly defined.
A further advantage is that the capacitor has a first predefined capacitance and a second predefined capacitance as a function of a predefined electrical voltage between the first connection and the second connection. As a result, it is possible to determine the operating frequency largely independently of the distance of the ground lines of the coplanar waveguide by dimensioning the first and second electrically conductive connections, in particular, and the dielectric layer between these two. The insertion attenuation (loss) is also adjustable as a result of this.
It is a further advantage that the first connection forms and inductor in series with the capacitor between the signal line and the ground lines. This makes it possible to provide different forms and dimensions for the first connection, so that the inductance resulting from the first connection is largely predefinable.
Furthermore, it is advantageous that the common impedance of the first capacitor and the inductor at an operating frequency essentially corresponds to their ohmic resistance. As a result, it is possible to achieve particularly significant insulation, i.e., a particularly large reflection coefficient, when the short-circuiting switch is switched off.
Another advantage is that approximately 77 GHz or approximately 24 GHz are provided as the operating frequency. This makes it possible to use the device of the present invention for ACC (adaptive cruise control) or SRR (short range radar) applications.
In addition, it is advantageous that the predefined length is provided such that reflections at a junction between the signal line and the second connection compensate for each other. As a result, the insertion attenuation of the switch and, thus, the adaptation in the on state are improved.